1. Field of the Invention
The present invention relates to a liquid crystal display apparatus and a chip mounted wiring substrate suitable for the liquid crystal display apparatus.
2. Description of the Related Art
In late years, a chip mounted wiring substrate (or chip-on flexible printed circuit substrate: hereinafter it is abbreviated as COF), which enables the miniaturization of wiring pitch responding to the miniaturization of the pitch of a driver IC, is used for assembling of the liquid crystal display apparatuses. The COF has a flexible printed circuit substrate (FPC) that connection wirings are formed on a base film and a driver IC is mounted on the FPC.
In case of manufacturing the liquid crystal display apparatuses in a factory in large quantities, as described in the prior arts JP 3-231228A, JP 9-218420A or JP 2007-123344A, for example, positioning marks are formed on both of the COF and the liquid crystal display panel, and the COF is fixed on the liquid crystal display panel by thermo-compression bonding or the like with recognizing the positioning marks by an automated machine. Thereby, the liquid crystal display panel and the COF are aligned with high precision. By the way, when really installing the COF to the liquid crystal display panel, it is necessary to superpose wiring electrodes formed on the COF above cell electrodes (transparent electrodes) formed on the liquid crystal display panel. However, the base film of the COF extends in each direction when it is installed by thermo-compression bonding, so that arrangement pitch of the wiring electrodes of the COF before the thermo-compression bonding is selected to be narrower/smaller that the arrangement pitch of the COF after the thermo-compression bonding in consideration of the extension of the base film. When the COF is installed to the liquid crystal display panel by the thermo-compression bonding, the positioning marks on the COF are displaced from the original positions by the extension of the base film. However, since these positioning marks are dummy electrodes which are not actually used as wiring electrode, the existence of the positioning marks causes no problem.
However, when the COF is dismounted from the liquid crystal display panel to repair the liquid crystal display apparatus, the COF must be attached to the liquid crystal display panel again by manual labor of a worker. Specifically, the worker must locate the COF on the liquid crystal display panel so that the positioning marks of the COF are disposed just above the positioning marks of the liquid crystal display panel and performs the thermo-compression bonding with keeping the posture. However, it is really very difficult and takes long time to perform the thermo-compression bonding by manual labor from a practical standpoint. In addition, although the wiring electrodes of the COF are arranged to have equal width and space, the cell electrodes of the liquid crystal display panel are not necessarily arranged to have equal width and space. Thus, if the width of the cell electrodes of the liquid crystal display panel is wider than that of the wiring electrodes of the COF, when the wiring electrodes formed on the COF are located above the cell electrodes of the liquid crystal display panel, the wiring electrodes may be blinded by the cell electrodes. Consequently, it is difficult to judge whether the COF is precisely positioned on the liquid crystal display panel or not by visual check.
In addition, JP 2005-284004A discloses a conventional technology which enables to make a picture frame of a liquid crystal display apparatus narrower. Pitch of the wiring electrodes of the COF is made narrower than that of the wiring electrodes of the liquid crystal display panel, and end portions of the wiring electrodes of the COF and the wiring electrodes of the liquid crystal display panel are respectively arranged on forty-five degree slanted lines, for example. The wiring electrodes of the COF and the wiring electrodes of the liquid crystal display panel are connected by junction circuits arranged in parallel with sides of the liquid crystal display panel. Since this technology is based on the premise that the wiring electrodes of the liquid crystal display panel are arranged to have equal width and space, it cannot solve the above mentioned problems.